H YDKOCEI'HA L I 'S. 



883 



cranial tumour — is entirely absent (Fig. 97). In other instances, and 

 particularly in the Foal, a kind of bony arch extends from the nasal to 

 the occipital bones, in the direction of the saggital suture, with only 

 here and there, on each side, small osseous patches from the parietal or 

 temporal bones, which adhere to the dura mater. 



Fig. 97. 

 Skull or a Hydbockphalic Calk : the Roof oi- thk Cranium i.v abse.vt. 



The tumour is always entirely covered by intact, though sometimes 

 Tery thin skin, to which the hair is ordinarily attached, and is indeed 

 at times longer than usual, especially at the sides. This often makes 

 the animal appear as if it wore a high fur cap (Fig. 99). 



Owing to the great development of the forehead, the upper jaw appears 

 to be shorter than usual ; and, indeed, it will be found that it is really 

 so (Fig. 96). 



Fig. 98. 



Skull of a HrnRotErHALic Foal: the Cranial K<x)f i.i DEKicreNT 

 AT THK Sides. 



When the cranial cavity is opened and the dura mater incised, there 

 is found a quantity — varying with the dimensions of the tumour — of 

 limpid, colourless, or slightly yellow or greenish serum. 



The quantity of fluid varies considerably, but it is generally from two 

 to four pints in the Foal and Calf. Eainard estimated the quantity of 

 fluid that had been contained in the skull of a Calf sent to him, at two 



